Absence of bowel opening is common among critically ill patients. Neostigmine can be used to achieve stool passage after other treatments have been ineffective. Here, we report a case of cardiac arrest complicating neostigmine use in a 16-year-old woman with cerebral palsy who was being treated in the intensive care unit after orthopaedic surgery. Bradycardia is a recognised complication of neostigmine administration; however, cardiac arrest has not been reported previously.